The present invention relates to a light transmission device that transmits a light flux via an optical fiber. In particular, the present invention relates to a light transmission device in which reflected light does not return to a light emitting element.
In a particular example, a multi-beam scanning optical device is provided with a light transmission device that includes a plurality of semiconductor lasers and a plurality of optical fibers. Light fluxes emitted from the semiconductor lasers enter into respective optical fibers, and are transmitted from exit ends of the optical fibers. The light fluxes exiting from the optical fibers are deflected by a polygon mirror and converged on an image surface through a scanning lens to form a plurality of scanning lines per scan.
However, in a conventional system, a part of a light flux emitted from a semiconductor laser may return back to an semiconductor laser due to reflection by the incident end surface of the optical fiber, causing the oscillation of the semiconductor laser to be unstable.
In particular, the oscillation mode of the semiconductor laser may change from a mono-mode to a multi-mode or the width of the oscillation wavelength may widen. Since a scanning optical system is generally not corrected for chromatic aberrations due to the generally limited wavelength of the semiconductor laser emissions, a change of the oscillation wavelength may result in a loss of the desired diameter of the beam spot on the image surface due to longitudinal chromatic aberration and may result in a change in the length of the scanning line due to lateral chromatic aberration. Variations in the diameter of the beam spot and the length of the scanning line decrease the accuracy of the image formed by the scanning lines, particularly at high resolutions.